MP2932 - 6-PHASE PWM CONTROLLER WITH 8-BIT ADC CODE

MP2932 Rev.1.02

www.MonolithicPower.com

14

4/30/2012

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© 2012 MPS. All Rights Reserved.

At the beginning of an over-voltage event, all

PWM outputs are commanded low instantly

(>20ns). The Intelli-phase LS-FET is turned on.

When the VDIFF voltage falls below the DAC +

75mV, PWM signals enter a Hi-Z state, and the

SD pin is pulled low to turn off the Intelli-phase.

If the over-voltage condition reoccurs, the

MP2932 will again command the LS-FET to

turn on. The MP2932 will continue to protect the

load in this way as long as the over-voltage

condition occurs.

Once an over-voltage condition is detected,

normal PWM operation ceases until the

MP2932 is reset. Cycling the voltage on

EN_PWR, EN_VTT or VCC below the POR-

falling threshold will reset the controller. Cycling

the ID codes will not reset the controller.

Over-current Protection (OCP)

MP2932

has

two

levels

of

over-current

protection. Each phase is protected from a

sustained over-current condition by limiting its

peak current, while the combined phase

currents are protected on an instantaneous

basis.

In instantaneous protection mode, the MP2932

compared with a constant 85µA reference

exceeds 85µA, a comparator triggers the

converter to shutdown. At the beginning of

over-current shutdown, the controller places all

PWM signals in a Hi-Z state within 20ns to turn

off the Intelli-phase. The system remains in this

state about 12ms. If the controller is still

enabled at the end of this wait period, it will

attempt a soft-start. If the fault remains, the

hiccup mode will continue indefinitely until

either controller is disabled or the fault is

cleared.

OUTPUT VOLTAGE

OUTPUT CURRENT

0A

0V

Figure 9—Over-current Behavior in HICCUP

Mode. Fsw = 600kHz

For

the

individual

channel

over-current

protection, the MP2932 continuously compares

the sensed current signal of each channel with

the 120µA reference current. If one channel

current exceeds the reference current, MP2932

will pull PWM signal of this channel to low for

the rest of the switching cycle. This PWM signal

can be turned on next cycle if the sensed

channel current is less than the 120µA

reference current. The peak current limit of

individual channel will not trigger the converter

to shutdown.

Thermal Monitoring (VR_HOT/VR_FAN)

There are two thermal signals to indicate the

temperature status of the voltage regulator:

VR_HOT and VR_FAN. Both VR_FAN and

VR_HOT pins are open-drain outputs, and

external pull-up resistors are required. Those

signals are valid only after the controller is

enabled.

The

VR_FAN

signal

indicates

that

the

temperature of the voltage regulator is high and

more cooling airflow is needed. The VR_HOT

signal can be used to inform the system that the

temperature of the voltage regulator is too high

and the CPU should reduce its power

consumption.